Coolant leak

[cameyer]

ok so here is the issue, i have a 64 k10 with a 327 from a 68 c20 and i am losing coolant out of the overflow tube like crazy. I have checked the oil and no coolant seems to be making it in there and the oil cap is clean so I dont think it would be the head gasket but i dont know what else it could be. The truck isnt overheating at runs at a normal temperature but i will fill the coolant up drive a few mile to the store mike up some groceries come back outside and find a puddle of coolant under the truck. None of the hoses are leaking and i cant see any obvious leaks other than the coolant draining from the over flow tube. anyone have any ideas?

[70inline6]

Are you overfilling the radiator, or, is the radiator right for your engine application. The stock radiators/cooling systems back when these were build didn't work off the 'coolant recovery system' method. "Full" on a radiator was when the coolant was about an inch below the bottom of the filler neck, not at the bottom of the neck. The void allows for fluid expansion when it gets warm.

OTOH, if you still have a I6 radiator in your truck, you have a greater volume of fluid now, and there may not be enough room in the system (when topped off) to allow for the expansion.

If it's cooling fine otherwise (as you say), try leaving that 1-inch void in the top of the radiator and see if that helps.

[Sharps40]

I discovered this the hard way, constantly topping off then took some good advice, went to Advance, bought the $15 coolant recovery tank, mounted it on the Driver side inner fender above the heater hoses and havn't had to add coolant in 8 months. One of the better 30 minute jobs I've accomplished.

[tincan1966]

As most people do not realize there are 2 types of radiator caps, as well. For closed system(with recovery tanks) and open. Most parts store people aren't old enough to know the difference and sell you a "chevy radiator cap".
As recommended above, keep the coolant level about an inch below the filler neck, install the correct radiator cap-I think it should be a 13-14 lb and see if that cures your coolant loss.
Adding a recovery tank with the correct cap is a real good idea, as an upgrade, too. It also keeps your truck from marking it's territory.

[63burban]

I usually fill the radiator and let it push out what it doesn't need, my 65 is happy with about a half inch above the core.Been running that way for close to 20 years. She's a happy little 230.

Laws of physics, expansion and contraction

[1966shortwide]

I had same problem on my 1966 with a 350 engine not overheating, just spitting out after driven and parked ,bought a new gm radiator cap, fixed the problem. I had bought parts house's cap's before ,same problem. you can tell the difference in tightness and quality just by installing it, compared to part's house cap. Also, keep your coolant level as mentioned above.

[cameyer]

Thanks for the help! I think I'll try a new cap first. I keep filling the radiator up just an inch below the neck and it looks like a larger after market radiator made my griffin so I'm hopping the cap is the issue
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[63burban]

Did you have the cooling system open for any reason ? May have air in the system.

[cameyer]

I just got the truck a few months ago and I have never had it open. Who knows about the previous owner though
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[jsdoyle]

I've seen water pumps leak when they are going bad. Real hard to see where it's coming from sometimes. Weep hole on bottom of pump is a possibility.

[61_FL_Apache]

Originally Posted by tincan1966

As most people do not realize there are 2 types of radiator caps, as well. For closed system(with recovery tanks) and open. Most parts store people aren't old enough to know the difference and sell you a "chevy radiator cap".
As recommended above, keep the coolant level about an inch below the filler neck, install the correct radiator cap-I think it should be a 13-14 lb and see if that cures your coolant loss.
Adding a recovery tank with the correct cap is a real good idea, as an upgrade, too. It also keeps your truck from marking it's territory.

Would you have pics of the two different caps? I was not aware that there was two different ones.

[shortbed70]

Originally Posted by 70inline6

Are you overfilling the radiator, or, is the radiator right for your engine application. The stock radiators/cooling systems back when these were build didn't work off the 'coolant recovery system' method. "Full" on a radiator was when the coolant was about an inch below the bottom of the filler neck, not at the bottom of the neck. The void allows for fluid expansion when it gets warm.

OTOH, if you still have a I6 radiator in your truck, you have a greater volume of fluid now, and there may not be enough room in the system (when topped off) to allow for the expansion.

If it's cooling fine otherwise (as you say), try leaving that 1-inch void in the top of the radiator and see if that helps.

Yup! I kept topping mine off and it would just leak out till 1" or so below the neck! Now no problems... New cap won't hurt though..
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